React is a Javascript framewowrk for content presentation. I've never used React because using something release by Facebook felt a little, well, greasy. That intuition is substantiated by this post. React is released under a 'BSD + patents' license. It looks like open source. But the license to use it is instantly revoked if you sue Facebook. "Bottom line: Open Source is not a “quid pro quo” trade. Open Source is about creating communities to build better software together. It should never be used as a marketplace to exchange rights."